The present disclosure relates to a B-pillar for a motor vehicle body, comprising a sheet metal formed part having a head portion, a central portion and a base portion, and having an inner side and an outer side, wherein the head portion, on the inner side, comprises a connecting region for connecting the B-pillar to a roof region of the motor vehicle body, wherein the base portion is configured for connecting the B-pillar to a sill region of the motor vehicle body, wherein the central region extends between the head portion and the base portion and defines a longitudinal direction of the B-pillar, wherein the sheet metal formed part comprises at least in the central portion a hat profile such that on the inner side a hollow chamber for receiving vehicle attaching parts is formed; and a fibre composite part having an upper portion, a central portion and a lower portion, wherein the lower portion ends in the central portion of the sheet metal formed part. Furthermore, the present disclosure also relates to a motor vehicle body having such a B-pillar.
It is known to produce B-pillars using hybrid construction in which metallic formed parts of the B-pillar are in areas reinforced by a fibre-reinforced composite material for the purpose of providing more light-weight B-pillars having an improved crash behaviour. DE 10 2006 027 546 A1 shows a multi-leaf B-pillar consisting of sheet metal formed parts that are reinforced, in the central region of the B-pillar, with a crash protection reinforcement part for the purpose of protecting the passengers in the case of a side impact. The reinforcement part consists of a fibre-plastic composite. DE 10 2012 023 653 A1 proposes a B-pillar having an inner closing part made out of a flat sheet blank, wherein a lightweight part made out of fibre-reinforced plastic is placed on the outside of the inner closing part. The fibre composite part extends along the entire length of the inner closing part.
Disclosed herein is a weight-reduced B-pillar that comprises a high degree of stiffness and meets the requirements of demanding crash scenarios. Further provided is a weight-reduced motor vehicle body that comprises a high degree of stiffness and meets the requirements of demanding crash scenarios.
In a B-pillar of the above-mentioned type the fibre composite part is attached to the outer side of the sheet metal formed part, wherein the head portion of the sheet metal formed part comprises a supporting region at the outer side, and wherein the upper portion of the composite fibre part comprises a contact region that laterally embraces the supporting region and is supported against same in the longitudinal direction of the B-pillar.
The B-pillar is a load-bearing vehicle pillar which, in the built-in condition, connects a roof region of the motor vehicle body to a sill region of the motor vehicle body. If reference is made to the “built-in condition”, this means the condition in which the B-pillar is built in, i.e., installed in, the motor vehicle body between the roof region and the sill region. Terms like “lower”, “upper” or “central” refer to spatial information with respect to the B-pillar in the built-in condition at the motor vehicle body.
As disclosed herein the fibre composite part is integrated into the B-pillar as a supporting and load-bearing structural element of the vehicle body. For this purpose, the fibre composite part is supported on the head portion of the sheet metal formed part, wherein, in the built-in condition, the upper portion of the fibre composite part axially, i.e., in the longitudinal direction of the B-column, overlaps with the roof region of the vehicle body, more particularly with a roof rail extending in the direction of driving. This results in a flux of force from the roof region via the composite fibre part into the sill region. In the built-in condition, the supporting fibre composite part is loaded by push loading and pull loading, and supports the roof region against the sill region. As a result of the greater strength of the fibre composite part relative to the sheet metal formed part, the fibre composite part accommodates a greater part of the load bearing function of the B-pillar than the sheet metal formed part, because, depending on the design of the fibre matrix structure, the ratio between the strength of the fibre composite part and the sheet metal formed part is about 5:1.
In the lower portion, the fibre composite part ends above the base portion. Compared to the sheet metal formed part, the fibre composite part comprises a lower elongation at break, which is the reason why the fibre composite part, upon introduction of load, gives way elastically up to a certain degree, but breaks when this degree is exceeded. Therefore, in order to provide a deformable zone at transition from the B-pillar to the sill region and/or in the door entrance area, the base portion of the B-pillar is formed by the sheet metal formed part only, thus allowing, in the case of a crash, plastical deformation. Hence, in the built-in condition, the forces acting on the fibre composite part in the lower region of the B-column are introduced entirely via the base portion of the sheet metal formed part into the sill region, so that, in the lower region of the B-pillar, a flux of force from the fibre composite part via the base portion of the sheet metal formed part into the sill region is achieved.
Furthermore, the fibre composite part is placed from outside onto the outer surface of the sheet metal formed part. In this way, the fibre composite part is arranged on the pressure-side of the sheet metal formed part, so that, in the case of a side impact, the fibre composite part is pushed against the sheet metal formed part. By integrating the fibre composite part as a supporting or load-bearing structural element on the pressure-side of the B-pillar, the fibre composite part can unbend or straighten up in the case of a side impact. If, in the case of a crash, the acting crash energy remains below the breaking force of the fibre composite part, after relief of energy, the fibre composite part returns back into its original built-in situation. In this way, the fibre composite part can flex elastically, virtually breathe, and can release the absorbed energy. As a result the present B-pillar provides a weight reduced and highly stressable vehicle pillar that has exactly two supporting or load-bearing structural elements, i.e., the sheet metal formed part and the fibre composite part.
In the built-in situation both the sheet metal formed part and the fibre composite part are integrated load-bearing structural elements of the motor vehicle body into the overall system of the vehicle.
According to one aspect of the present invention, the supporting region of the sheet metal formed part is configured to be wedge-shaped. Accordingly, the contact region of the fibre composite part can be widened upwards or from the bottom to the top, further can be configured to be fan-like. Thus, an especially stable axial support of the fibre composite part on the head portion of the sheet metal formed part is achieved. In the region of contact, the fibre composite part can be pushed and/or laid onto the supporting region of the sheet metal formed part.
Furthermore, in the region of contact, the fibre composite part can be connected to the supporting region of the sheet metal formed part by connecting means. Thus, the connection between the fibre composite part and the sheet metal formed part is additionally strengthened in the region of contact. The connecting means can be rivets for example. In addition, the fibre composite part can be connected to the sheet metal formed part in the region of contact in a material-locking way and/or adhesive bond, e.g., particularly glued.
Furthermore, at least in its central portion, the fibre composite part can comprise a cupped or shell-like profile whose cross-section, at least in some portions, is U-shaped. Furthermore, the fibre composite part can surround the sheet metal formed part from the sides wherein the sheet metal formed part can have a hat-shaped profile at least in its central portion. Thus, the stability of the B-pillar is increased. At least in its central portion, the composite fibre part can form-lockingly or positive-lockingly rest against the sheet metal formed part.
The fibre composite part can be connected to the central portion of the sheet metal formed part by fixing means, e.g., bolted connections which are designed to attach motor vehicle components being held at the B-pillar. Thus, the fixing means can have a double function, not only to connect the fibre composite part to the sheet metal formed part, but also to fix the motor vehicle components, e.g. a closing wedge for the front door, a door lock, a door hinge, a rear door holding element, receiving means for a belt roller or belt tightening means, to the B-pillar.
Furthermore, the fibre composite part can comprise metallic connecting elements which are partly embedded into the fibre composite and protrude from the fibre composite part with free end regions. At its free end regions, the fibre composite part can be material-lockingly connected to the sheet metal formed part, e.g., by welding, for instance by spot welding or laser welding. The free end regions can protrude from the fibre composite of the fibre composite part in the longitudinal and/or transverse direction. Furthermore, the free end regions of the connecting elements can be formed of a plurality of narrow, bar-like feet or of one or several flanges extending in the longitudinal direction.
Furthermore, the fibre composite part can comprise at least one reinforcing insert embedded into the fibre composite. Thus, the crash behaviour of the fibre composite part can be modified. The reinforcing insert can be a metallic sheet metal part. For instance, it can be embedded into the structure of the surrounding fibre material layers of the fibre composite part in a form-locking and load-bearing way by braiding fibre strands. Because of its surface structure, i.e. its roughness and/or its surface coating, the reinforcing insert can be load-bearingly embedded into a matrix surrounding the fibres of the fibre composite material. A resin matrix is particularly suitable for a matrix system. The embedded reinforcing insert can be produced from a cold- or hot-formed high-strength or super high strength steel. Furthermore, the reinforcing insert can comprise a variable thickness or wall thickness in the longitudinal direction and/or in the transverse direction extending transversely, more particularly, perpendicularly to the longitudinal direction of the B-pillar. The reinforcing insert is able to absorb the compressive stresses resulting from a crash energy within the fibre composite part in an optimum way, and thus is able to improve the properties of the fibre composite part in respect of tensile strength.
Furthermore, the fibre composite part, at least in its lower portion, can rest on the sheet metal formed part in such a way that the fibre composite part is supported against the sheet metal formed part in longitudinal direction. In this way, the load bearing behaviour of the fibre composite part as a supporting structural element of the B-pillar is improved.
Furthermore, in the upper region of the base portion and/or in the lower end region of the central portion, the sheet metal formed part can comprise a hardened high-strength area. Since the fibre composite part is integrated into the B-pillar as a supporting structural element, the composite fibre part can straighten when it is pushed towards the formed sheet metal part during a side crash. Thereby, the lower longitudinal end of the fibre composite part can be pushed into the sheet metal formed part. This can result in the collapse of the sheet metal formed part. Due to the high-strength area, the sheet metal formed part said collapse can be prevented. However, the hardened high-strength area of the sheet metal formed part does not extend beyond the door entrance region of the base portion which, on the contrary, can be provided in the form of a soft deformation zone to be able to deform plastically in a crash scenario.
The sheet metal formed part can be produced from a steel plate. The steel material can be, for instance, boron steel, in particular 22MnB5, wherein other hardenable steel materials are also possible. The sheet metal formed part can also be a lightweight component made of magnesium or aluminium. In its different regions, the sheet metal formed part can comprise differently rolled sheet thicknesses, different steel and/or aluminium alloys, different surface coating conditions and different tempered conditions. In order to connect the sheet metal formed part with the vehicle body and/or adjacent components within the vehicle body, for instance beading and/or spot welding and/or laser welding can be used.
Unexpectedly, it has been found that by combining a hot-formed and at partially hardened sheet metal formed part with the fibre component part, the B-pillar comprises a sufficiently high degree of stiffness for meeting the requirements of demanding crash scenarios. Even more, the B-pillar comprises a spring-like and in the elastic state deformable basic shape. Hence, cold-formed parts, which are commonly considered as being capable of bearing high loads, are not necessary. However, in principle, the sheet metal formed part could also be a cold-formed part. As a benefit of the integration of the fibre composite part as a supporting structure element, the hot-formed and at least partially hardened sheet metal formed part can be thin-walled.
The sheet metal formed part can be produced from a tailor rolled blank or a tailor welded blank, and thus, along its length, comprises a variable sheet thickness. Thus, the sheet metal formed part can be specifically and locally adjusted. Any zones which are subjected to less stress can comprise a lower sheet thickness compared to higher stressed zones of sheet metal formed parts. For example, the sheet thicknesses of the sheet metal formed part can vary between 0.7 and 3 mm (millimeters). More particularly, the sheet metal formed part can have a sheet thickness in its head portion of 1 mm to 3 mm, and in its central portion of 0.7 mm to 2 mm, and in the base portion of 1 mm to 3 mm. Furthermore, in addition to commonly provided recesses, which serve to mount motor vehicle components, the sheet metal formed part more particularly in its central portion can comprise further recesses for specifically reducing the weight of the sheet metal formed part. The resulting weakening of the sheet metal formed part is deliberately accepted, because it is not the sheet metal formed part, but the fibre composite part which bears the main load of the B-pillar. This means that more than half the load acting on the B-pillar in the longitudinal direction is supported by the fibre composite part.
Hot-forming refers to the process of forming metals above the recrystallisation temperature. Hot-forming and hardening can take place in one process in a press hardening tool. This combined process of forming and hardening is also referred to as press hardening. For instance, the sheet metal formed part is produced from a blank which, prior to being hot-formed, is heated up to at least 800 to 850 degrees Celsius, then is inserted into a forming tool and is formed in a hot condition, and by contacting the forming tool, it is quickly cooled. The forming tool can be force-cooled from the inside. The process of cooling the sheet metal formed part in the forming tool can take place within approximately 15 seconds or less to approximately 200 degrees, for example. Besides to the above-described press hardening process, the sheet metal formed part can also be hardened in a different way. According to a possible embodiment, the hardened sheet metal formed part can also comprise local soft zones which, in the case of a crash, can serve in particular as defined deformation zones. The mechanical properties of the soft zones can be configured to meet certain requirements. For example, soft zones being configured as failure areas can comprise an elongation of break value that is clearly higher than an elongation of break value of the hardened base material. Preferably, the elongation at break in the soft zones amounts to more than 10%, more particularly 10 to 15%. Contrary, the elongation of break of the hardened base material of the lower formed part can amount to approximately 4% to 7%.
Furthermore, the sheet metal formed part can be coated, e.g., by an aluminium-silicon-alloy or zinc coating to serve as corrosion protection and also to avoid scaling during the hot-forming process. The sheet metal formed part can be coated before and/or after the hot-forming process. When coating takes place before the hot-forming process, it is possible, on the one hand, to coat a strip material out of which the sheet metal formed part can be produced or, on the other hand, to coat the blank itself. When coating takes place after the hot-forming process, the sheet metal formed part being formed and in particular already hardened, can be coated.
The fibre composite part can contain carbon fibres and/or glass fibres and/or even aramide fibres and/or metallic fibres. The fibres of the fibre composite material can be embedded in a resin matrix, more particularly in an epoxy matrix. More particularly, the fibre content can also comprise a combination of the above-mentioned fibres. Furthermore, by axial or multi-axial alignment of the fibres it is possible to modify the fibre composite with regard to the respective application areas and required crash properties. In addition to the selections of fibres or the fibre alignment, the fibre composite part can also be adapted by locally different wall thicknesses. This can be achieved by varying the number of fibre layers. In this way, the crash behaviour of the B-column can be adjusted or varied section by section.
The fibre composite part can be connected to the sheet metal formed part by gluing and/or nailing and/or bolted connections. Between the sheet metal formed part and the fibre composite part it is possible to provide a blocking or uncoupling layer, for instance made out of a glue in order to prevent contact corrosion between the fibre composite part and the sheet metal formed part. In order to achieve a stable connection between the two supporting structural elements, the fibre composite can be connected to the sheet metal formed part in a planar way.
In one example, an outer edge of the fibre composite part can be spaced from an outer edge of the sheet meal formed part in such a way that between the outer edge of the fibre composite part and the outer edge of the sheet metal formed part, the sheet metal formed part forms a single-layered connecting flange of the B-pillar for connecting a door seal and/or an outer vehicle skin and/or a glass panel with the sheet metal formed part. In this way, the sheet metal formed part is the only partner to be connected with further components which do not form part of the B-pillar. Thus, the outer vehicle skin can be welded to the single-layered connecting flange. The fibre composite part does not extend beyond the connecting flange. In a preferred embodiment, the sheet metal formed part forms two spaced, radially outer connecting flanges that, in the longitudinal direction, preferably extend at least along the entire length of the central portion.
To ensure that the connecting flange can be as wide as possible, the sheet metal formed part can comprise two opposed side walls, with the fibre composite part resting on outer shoulders of the side walls. The side walls adjoin radially inwards the respective connecting flange.
The sheet metal formed part extends along the entire length of the B-column. Typically, a B-column of a conventional passenger car has a length of about 1.30 to 1.50 m (meters). The length of the head portion merely serving to connect the sheet metal formed part to the roof region of the motor vehicle body and supporting the fibre composite part is smaller than or equal to 15% of the length of the sheet metal formed part. The head portion can be flange-like. More particularly, the head portion can be U-shaped in the longitudinal section and, in the built-in condition, embrace the roof rail from the outside. At the transition to the central portion, the lower head portion can comprise a tapered section and/or the upper central portion can comprise a widened section. The length of the base portion comprising a deformation zone of the B-pillar and serving for connection to the sill region, can be smaller than or equal to 25% of the length of the sheet meal formed part. The base portion can be flange-like and, in the built-in condition, embrace the sill region from the outside. More particularly, the base portion can comprise a U-shaped cross-section and, at the transition to the central portion, can comprise a tapered portion. Alternatively, the base portion can comprise a connecting bar that can engage with a recess in the sill region coming from above for the purpose of connecting the B-pillar in the built-in condition via a plug-in connection with the sill region. Between the head portion and the base portion there extends the central portion which commonly, for passenger protection purposes, is high-strength. The length of the central portion is approximately 60% to 90% of the length of the sheet metal formed part.
The fibre composite part starts within the height of the head portion and ends in the central portion of the sheet metal formed part. Accordingly, the length of the fibre composite part is between 50% to 90% of the length of the sheet metal formed part. Using the above-mentioned length of the sheet metal formed part between 1.30 and 1.5 m as an example, the fibre composite part can thus comprise a length of approximately 0.65 to 1.35 m. The length of the head portion of the sheet metal formed part can be smaller than or equal to 0.23 m and the length of the base portion of the sheet metal formed part can be smaller than or equal to 0.37 m.
In order to provide an especially lightweight B-pillar with a small number of parts, the fibre composite part can be the outermost part of the B-pillar. I.e. on the B-pillar outside facing away from a vehicle interior, the fibre composite part is not covered by a supporting structural element of the B-pillar. Independently of the above, smaller sheet metal parts for mounting or connecting the vehicle parts such as a closing wedge for the front door, a door lock, a door hinge or a rear door holding element can be arranged on the outside of the fibre composite part, which faces away from the vehicle interior. In the built-in condition, the fibre composite part, in turn, can be covered by the outer vehicle skin that is usually fixed to the vehicle body only after completion of same. In order to provide an especially lightweight vehicle body, the fibre composite part can be visible from the outside in the built-in condition, so that the fibre composite part in the built-in condition of the B-pillar is not, or at least not fully, covered by the outer vehicle skin.
Furthermore, the sheet metal formed part can be the innermost formed part of the B-pillar. I.e. on the inside of the B-pillar facing the vehicle interior, the sheet metal formed part is not covered by any structural element of the B-pillar. By combining the sheet metal formed part with the fibre composite part, there is no need for a closing plate known from the state of the art, also referred to as cover or inner plate.
A further solution to the above-mentioned problem is achieved by providing a motor vehicle body having the above-mentioned B-pillar. Because of the presently disclosed motor vehicle body, there are achieved the same advantages as obtained in connection with the disclosed B-pillar, so that, briefly, reference can be made to the above descriptions. It is understood that all the above-mentioned embodiments of the B-pillar can be used for the motor vehicle body, and vice versa. Overall, the presently disclosed motor vehicle body is characterised by a reduced number of parts and a reduced weight, further, it comprises a high degree of stiffness and is able to meet the requirements of demanding crash scenarios.
In particular, the fibre composite part of the B-pillar in the motor vehicle body is visible from the outside. In other words, the fibre composite part of the B-pillar is not, or not fully, covered by the outer vehicle skin and, more particularly, is visible if the front door is open.